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"""
This module contains operator to move data from MySQL to Druid.
"""

from collections import OrderedDict
from tempfile import NamedTemporaryFile
from typing import Dict, Optional

import MySQLdb
import unicodecsv as csv

from airflow.hooks.hive_hooks import HiveCliHook
from airflow.hooks.mysql_hook import MySqlHook
from airflow.models import BaseOperator
from airflow.utils.decorators import apply_defaults


class MySqlToHiveTransfer(BaseOperator):
    """
    Moves data from MySql to Hive. The operator runs your query against
    MySQL, stores the file locally before loading it into a Hive table.
    If the ``create`` or ``recreate`` arguments are set to ``True``,
    a ``CREATE TABLE`` and ``DROP TABLE`` statements are generated.
    Hive data types are inferred from the cursor's metadata. Note that the
    table generated in Hive uses ``STORED AS textfile``
    which isn't the most efficient serialization format. If a
    large amount of data is loaded and/or if the table gets
    queried considerably, you may want to use this operator only to
    stage the data into a temporary table before loading it into its
    final destination using a ``HiveOperator``.

    :param sql: SQL query to execute against the MySQL database. (templated)
    :type sql: str
    :param hive_table: target Hive table, use dot notation to target a
        specific database. (templated)
    :type hive_table: str
    :param create: whether to create the table if it doesn't exist
    :type create: bool
    :param recreate: whether to drop and recreate the table at every
        execution
    :type recreate: bool
    :param partition: target partition as a dict of partition columns
        and values. (templated)
    :type partition: dict
    :param delimiter: field delimiter in the file
    :type delimiter: str
    :param quoting: controls when quotes should be generated by csv writer,
        It can take on any of the csv.QUOTE_* constants.
    :type quoting: str
    :param quotechar: one-character string used to quote fields
        containing special characters.
    :type quotechar: str
    :param escapechar: one-character string used by csv writer to escape
        the delimiter or quotechar.
    :type escapechar: str
    :param mysql_conn_id: source mysql connection
    :type mysql_conn_id: str
    :param hive_conn_id: destination hive connection
    :type hive_conn_id: str
    :param tblproperties: TBLPROPERTIES of the hive table being created
    :type tblproperties: dict
    """

    template_fields = ('sql', 'partition', 'hive_table')
    template_ext = ('.sql',)
    ui_color = '#a0e08c'

    @apply_defaults
    def __init__(  # pylint: disable=too-many-arguments
            self,
            sql: str,
            hive_table: str,
            create: bool = True,
            recreate: bool = False,
            partition: Optional[Dict] = None,
            delimiter: str = chr(1),
            quoting: Optional[str] = None,
            quotechar: str = '"',
            escapechar: Optional[str] = None,
            mysql_conn_id: str = 'mysql_default',
            hive_cli_conn_id: str = 'hive_cli_default',
            tblproperties: Optional[Dict] = None,
            *args, **kwargs) -> None:
        super().__init__(*args, **kwargs)
        self.sql = sql
        self.hive_table = hive_table
        self.partition = partition
        self.create = create
        self.recreate = recreate
        self.delimiter = str(delimiter)
        self.quoting = quoting or csv.QUOTE_MINIMAL
        self.quotechar = quotechar
        self.escapechar = escapechar
        self.mysql_conn_id = mysql_conn_id
        self.hive_cli_conn_id = hive_cli_conn_id
        self.partition = partition or {}
        self.tblproperties = tblproperties

    @classmethod
    def type_map(cls, mysql_type: int) -> str:
        """
        Maps MySQL type to Hive type.
        """
        types = MySQLdb.constants.FIELD_TYPE
        type_map = {
            types.BIT: 'INT',
            types.DECIMAL: 'DOUBLE',
            types.NEWDECIMAL: 'DOUBLE',
            types.DOUBLE: 'DOUBLE',
            types.FLOAT: 'DOUBLE',
            types.INT24: 'INT',
            types.LONG: 'BIGINT',
            types.LONGLONG: 'DECIMAL(38,0)',
            types.SHORT: 'INT',
            types.TINY: 'SMALLINT',
            types.YEAR: 'INT',
            types.TIMESTAMP: 'TIMESTAMP',
        }
        return type_map.get(mysql_type, 'STRING')

    def execute(self, context: Dict[str, str]):
        hive = HiveCliHook(hive_cli_conn_id=self.hive_cli_conn_id)
        mysql = MySqlHook(mysql_conn_id=self.mysql_conn_id)

        self.log.info("Dumping MySQL query results to local file")
        conn = mysql.get_conn()
        cursor = conn.cursor()
        cursor.execute(self.sql)
        with NamedTemporaryFile("wb") as f:
            csv_writer = csv.writer(f, delimiter=self.delimiter,
                                    quoting=self.quoting,
                                    quotechar=self.quotechar,
                                    escapechar=self.escapechar,
                                    encoding="utf-8")
            field_dict = OrderedDict()  # type:ignore
            for field in cursor.description:
                field_dict[field[0]] = self.type_map(field[1])
            csv_writer.writerows(cursor)
            f.flush()
            cursor.close()
            conn.close()
            self.log.info("Loading file into Hive")
            hive.load_file(
                f.name,
                self.hive_table,
                field_dict=field_dict,
                create=self.create,
                partition=self.partition,
                delimiter=self.delimiter,
                recreate=self.recreate,
                tblproperties=self.tblproperties)
